Agreed, especially with ethanol becoming more and more part of it.
Yeah, steel is great for tanks, as it bends and recovers most of the time, aluminium and especially stainless really don't like being flexed about.
If it were me, if I hadn't already decided to go TD5 I'd be making a new steel tank with a nice thick bottom (maybe 5mm?) so there's no need for a tank guard, and the rest in 3mm, including the baffles.
But TD5 is WAAAY easier and cheaper.